Re: AC_SYS_LARGEFILE

[Sébastien Hinderer]

Hello,

Many thanks for your response.

Paul Eggert (2023/09/11 13:38 -0500):
> On 9/11/23 13:23, Russ Allbery wrote:
> > I suspect that the aswer to the original question is "don't worry about
> > it, just use AC_SYS_LARGEFILE, because no system you will build on will
> > need the CC modification anyway."
>
> Yes, that's the advice I'd give.

Investigation shows that using AC_DEFINE to define _FILE_OFFSET_BITS
won't work for the project because the definition would be read too
late, namely after the system headres have been included. This is
because, sadly, the project currently has the convention of including
system headers before its ocnfiguraiotn headers. It's not really
something that looks easy to change, or at least if we want to change it
it will take some time and require some care, because third-party code
is compiled using our headers and compiler options, so it is verly
likely that this third-party code also does include the systemheaders
before the configuraiton headers, which works currently because
-D_FILE_OFFSET_BITS=64 is passed on the command-line.

One option I am ocnsidering is to use themacro to determine wether the
macro needs to be defined and then use its result to determine whether
-D_FILE_OFFSET_BITS=64 should be addeed to the command-line or not. It
does not feel ideal but at least the logic would be reused from
Autoconf, which would be an improvement over the current situaiton where
the logic is poorly implemented in our configure script.

> One other caveat is that if you want to port to native Microsoft Windows
> (with either Mingw or not), Autoconf doesn't really support that. Gnulib has
> a largefile module that attempts to address that platform.

Good hint! Thanks!

Best wishes,

Seb.